Oxy aromatic polyamides and process for preparation



United States Patent 3,332,907 OXY AROMATIC POLYAMIDES AND PROCESS FOR PREPARATION Rudolph J. Angelo and Charles E. Berr, Wilmington, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed June 17, 1963, Ser. No. 288,534 6 Claims. (Cl. 260-47) This invention relates to novel shapeable or tractable polymeric compositions and, more particularly, to the preparation of the tractable polymeric compositions, their formation into shaped articles, and their conversion into substantially intractable polymeric articles. As used in the present specification, shapeable refers to the ability of the polymeric compositions to be shaped into useful structures by extrusion through dies, casting as films, coating on substrates, or by similar processing.

The outstanding physical and chemical properties of certain polymers make them extremely useful in the form of shaped structures such as films, filaments, tubing, etc. However, the same outstanding physical and chemical properties make it extremely difficult to shape these polymers into useful structures. One purpose of the present invention is to provide a group of polymeric compositions having satisfactory physical and chemical properties, but which can easily be formed into shaped structures. A further purpose is to select polymeric compositions which, in the form of shaped structures, can be converted into polymers having even more outstanding physical and chemical properties.

Specifically, the object of the present invention is to provide shapeable compositions of certain substituted polyamides. A further object is to provide shaped structures of these polyamide compositions. A still further object of the invention is to convert the polyamide structures to structures of polymers having even more desirable properties than the polyamides, e.g. structures of polybenzoxazoles. Other objects will appear hereinafter.

The objects are accomplished by a composition containing at least one polyamide having the following structural formula:

XO OX i l LM it 1.

R is an aromatic tetravalent radical; R is arylene; -X is selected from the group consisting of hydrogen,

wherein R being lower alkyl (up to six carbon atoms) and R R and R each being selected from the group consisting of hydrogen and R X being preferably hydrogen and R and wherein n is an integer sufficient to provide a film-forming polyamide, i.e. having an inherent viscosity of at least 0.3, preferably 0.5-5.0, as measured at 30 C. as a 0.5% solution in a suitable solvent, concentrated sulfuric acid. The polyamides for use in the composition of the present invention are solids with an undefined melting point.

Their infrared absorption spectra are characterized by Patented July 25, 1967 absorption bands at ca. 3.1 microns due to the N-H bond of the amide groups and at ca. 6.0 microns due to the C=O bond of the amide groups.

The process for preparing the polyamide compositions comprises reacting by mixing at least one organic diamine having the structural formula:

wherein R is an aromatic tetravalent radical each amino group of said diamine attached directly to a carbon atom of a ring of said aromatic radical ortho or peri to the carbon atom to which an OX is directly attached; with at least one halide-substituted dicarboxylic acid, or an anhydride of the dicarboxylic acid, or lower alloyl esters of the dicarboxylic acid, or phenyl esters of the dicarboxylic acid, preferably the halide-substituted ldicarboxylic acid having the structural formula:

wherein R is arylene; and Y is halogen, preferably chlorine,

In an organic solvent for at least one reactant, said solvent being inert to the reactants, for a time, preferably of at least 1 minute, and at a temperature below 275 C., sufficient to provide the corresponding polyamide.

It should be understood that one purpose of the process is to provide a composition that can be shaped into useful objects. In determining a specific time and a specific temperature for forming the polyamide of a specified diamine and a specified substituted acid, several factors must be considered. The maximum permissible temperature will depend on the diamine used, the acid used, the particular solvent, the percentage of polyamide desired in the final composition and the minimum period of time that one desires for the reaction. Temperatures up to 275 C. may be tolerated to provide shapeable compositions of the polyamide. The particular temperature below 275 C. that must not be exceeded for any particular combination of diamine, diacid-halide, solvent and reaction time to provide a reaction product composed of the shapeable polyamide will vary but can be determined by a simple test by any person of ordinary skill in the art.

The resulting polymeric hydroxy or alkoxy amide or the like can be cast or extruded into a film, filament, rod tube or other desired shape, or it can be used in solution as a coating composition. After shaping the composition composed predominantly of the polyamide, preferably still in the solvent, into a useful article, e.g. filament, film, tube, rod, etc., and drying the article, it'is preferred to convert the polyamide to another polymer to modify the properties of the shaped structure. Thus, the polyamide is converted to the corresponding polybenzoxazole by treatment to split out the elements of XOH, i.e. by heating at about 275-475 C., preferably 330-450 C. for a sufficient time, usually at least one hour, to effect such conversion.

The polybenzoxazoles of this invention find many ap plications in a wide variety of physical shapes and forms. Among the most significant of these forms are films and fibers. Films and fibers of this polymer not only possess excellent physical properties at room temperature, but retain their strength at elevated temperatures for prolonged periods of time. Because of the solubility of the polymer precursors, they can be processed into shaped articles such as films, fibers, tubes, rods, sheets and discs by conventional technique, and then converted into the final high-melting, relatively intractable cyclized polymers, the polybenzoxazoles.

The final shaped article may consist of the heterocyclic polymer alone or as a blend with other polymers and/ or modified with inert materials. Depending on their nature, the inert materials may be added before or after shaping. For example, fillers such as pigments, electrically conductive carbon black and metal particles, abrasives, dielectrics and lubricating polymers may be added conveniently to the intermediate polymer as such or to a solution of the intermediate polymer before shaping. Certain abrasives and electrically conductive materials are better added as surface layers. A cellular form or foam of the final polymer may be produced by adding a conventional blowing agent to the intermediate polymer, either alone or in combination with a filler, followed by heating to decompose the agent and cyclize the polymer units. Alternatively, cellular products can be made by dispersing bubbles (of air, carbon dioxide, nitrogen, etc.) into a melt or solution of the intermediate polymer before shaping and cyclization.

Instead of being shaped itself, the intermediate polymer can be used as a coating composition. Sometimes a melt of this polymer is suitable, but a solution generally is more useful. The liquid coating composition containing the polymer, either alone or modified by the addition of fillers and/ or foaming agents, may be applied by any of the usual techniques (doctoring, rolling, dipping, brushing, spraying) to a great variety of substrates. Such subtrates include copper, brass, aluminum, steel, and other metals in the form of sheets, fibers, Wires, screening; mineral structures such as asbestos; glass in the form of sheets, fibers, foams, fabrics, etc.; polymeric materials such as cellulosic materials (cellophane, wood, paper, etc.); polyolefins (polyethylene, polypropylene, polystyrene, etc.), polyesters (polyethylene terephthalate, etc.) polyamides, polyimides, perfluorocarbon polymers (polytetrafiuoroethylene, copolymers of tetrafluoroethylene with hexafiuoropropylene, etc.), polyurethanes, in the form of sheets, fibers, foams, woven and non-woven fabrics, screening, etc.; leather sheets; etc. The polymeric substrates can be metallized before coating, or treated with a conventional adhesive or other agent to improve surface receptivity. Films of the final cyclized polymer can be laminated to any of the above substrates, often with the aid of a commercially available adhesive.

Films formed from the polymer of this invention may be used wherever films have heretofore been used. They serve advantageously in wrapping, packaging and bunlling applications. Additionally, the film-forming polymer may be used in automobile and aviation interior hea-d linng materials, decorative trim, high temperature electrical nsulation, in the form of corrosion-resistant pipe, duct vork, containers and container linings, and the laminatng structures mentioned previously. In fiber form, the :olymer of the present invention offers possibilities for righ temperature electrical insulation, protective clothing and curtains, filtration media, packing and gusseting maerials, brake linings and clutch facings.

Hi the preparation of the shapeable compositions and he final polymer of the present invention it is essential hat the molecular weight be such that the inherent vis- :osity of the polymers be at least 0.3, preferably 0.5-5.0. The inherent viscosity is measured at 30 C. at a concenration of 0.5% by weight of the polymer in a suitable olvent. The suitable solvent for the purpose of the presnt invention has been chosen as concentrated sulfuric cid. The viscosity of the polymer solution is measured elative to that of the solvent alone and the natural logarithm where C is the concentration expressed in grams of polymer per milliliters of solution. As known in the polymer art, inherent viscosity is directly related to the molecular weight of the polymer.

The starting materials for forming the products of the present invention are at least one compound of the class: aromatic diacid halides, aromatic diacid anhydrides and aromatic diacid lower alkyl or phenyl esters and at least one compound of the class: bis(o-hydroxy) arylene diamines, bis(o-lower alkoxy) arylene diamines and similar diamines.

The most readily available diamine is 3,3-dihydroxybenzidine. This diamine may be obtained by demethylation of commercially available o-dianisidine with aluminum chloride according to the procedure described in U.S. Patent 2,497,248. Also operable and prepared similarly are other bis(ortho hydroxy amine phenyl) compounds and their derivatives of the structure.

where Y is any one of the following: carbon-carbon bond linking the two aromatic rings; a divalent hydrocarbon radical, i.e., alkylene or alkylidene; a divalent perhalocarbon radical, i.e. perfluoroalkylene or alkylidene; oxygen; sulfur; S0 CO; CONH; COO;

his (3 -hydroxy-4-amino biphenyl;

bis 3-methoxy-4-amino biphenyl;

1,2-bis (3 -hydroxy-4-aminophenyl ethane;

2,2-bis (3 -hydroxy-4-aminophenyl propane;

bis 3-hydroxy-4-aminophenyl) bis (trifluoromethyl) methane;

bis 3-hydroxy-4-aminophenyl ether;

bis (3 -hydroxy-4-aminophenyl) sulfide;

bis (3 -hydroxy-4-aminophenyl sulfone;

bis 3-hydroxy-4-aminophenyl ketone;

bis 3-hydroxy-4-aminophenyl methane;

N- (3 -hydroxy-4-aminophenyl -3 -hydroxy-4- aminobenzamide;

(3-hydroxy-4-aminophenyl -3 -hydroxy-4-aminobenzoate;

(3-hydroxy-4-aminophenyl) -3 -hydroxy-4-aminophenyl carbamate;

N,N-bis 3-hydroxy-4-aminophenyl urea;

bis 3-amino-4-hydroxyphenyl )ether;

bis (3 -amino-4-hydroxyphenyl) sulfide;

bis (3 -amino-4-hydroxyphenyl) sulfone;

bis 3-amino-4-hydroxyphenyl sulfoxide;

bis 3-amino-4-hydroxyphenyl) ketone;

bis 3-amino-4-hydroxyphenyl methane;

1,2-bis (3 -amino-4-hydroxphenyl ethane;

2,2-bis 3-amino-4-hydroxyphenyl) propane;

bis (3 -amino-4-hydroxyphenyl) dimethyl silane;

bis 3-amino-4-hydroxyphenyl dibutyl silane bis 3-amino-4-hydroxyphenyl methyl phosphine;

bis 3 -amino-4-hydroxyphenyl butyl phosphine;

1,5-diamino-2,6-naphthalene diol;

1,6-diamino-2,5-naphthalene diol; 2,5-diamino-1,6-naphthalene diol; 2,6-diamino-1,5-naphthalene diol; 1,6-diamino-2,7-dihydroxy naphthalene; 2,5-diamino-1,7-dihydroxy naphthalene; 1,7-diamino-2,6-dihydroxy naphthalene; 2,7-diamino-1,6-dihydroxy naphthalene; 2,7-diamino-3,6-dihydroxynaphthalene; 3,7-diamino-2,G-dihydroxynaphthalene; l,S-diamino-4,8-dihydrxynaphthalene; l,5-diamino-2,6-dihydroxy anthracene; 1,8-diamino-2,7-dihydroxy phenanthrene; 1,4-diamino-2,5-dihydroxy benzene; 1,3-diamino-4,6-dihydroxy benzene; bis(3-acetoxy-4-amino)biphenyl; bis 3-thionoacetoxy-4-amino) biphenyl; methyl carbonate ester'of bis(3-hydroxy-4-amino) biphenyl; bis 3- (ca-rboxymethyleneoxy) -4-amino biphenyl; bis(3-carbomethoxymethyleneoxy)-4-amino)biphenyl; bis( 3 (carbomethoxyethylideneoxy) -4-amino biphenyl bis(3-(carbomethoxyisopropylideneoxy)-4-amino) biphenyl; bis(3-thiocarbomethoxymethyleneoxy-4-amino) biphenyl; bis(3-dithiocarbomethoxymethyleneoxy-4-amino) biphenyl.

In the latter types of compounds, X is -CR R CO R CR R COSR and -CR R CS R respectively, in which R R and R are each hydrogen or lower alkyl. For the sake of simplicity these have been exemplified in the biphenyl series only. The corresponding derivatives of all the other hydroxy compounds shown above are also operable. Representative of the radicals provided by the diamines just disclosed are phenyl)ether; bis(3-chlorocarbonylphenyl)sulfide; bis(4- chlorocarbonylphenyl)sulfide; bis(3-chlorocarbonylphenyl)sulfone; and his (4-chlorocarbonylphenyl)sulfone. Representative radicals provided by this class include where Z is selected from the group consisting of alkylene of 1 to 3 carbon atoms, oxygen, sulfur, and SO Also operable are the lower alkyl or aryl esters of the foregoing aromatic acids as well as their anhydrides with fatty acids such as acetic acid and alpha-halogenated fatty acids such as trifluoroacetic acid, trichloroacetic acid, difiuoroacetic acid and dichloroacetic acid.

As mentioned previously, the reaction of any of these aromatic carboxylic acid derivatives with the hydroxy amines and their derivatives may be carried out in an inert solvent to form the polymeric hydroxy or alkoxy amide or the like. This polymeric intermediate can be shaped and after it is in the desired shape, converted into the corresponding polybenzoxazole by heating at a temperature above about 275 C. This conversion can be started if desired in a high boiling solvent such as diphenylmethane, and then finished by vigorous heating of the dry polymer. The reaction is aided by a current of inert gas such as nitrogen, or by operating in a vacuum, both of which help to remove the by-product water or alcohol. The structural formula of the resulting polybenzoxazole follows:

wherein provide a fihn forming The solvents useful in the solution polymerization process for synthesizing the polyamide compositions of the present invention are the organic solvents whose functional groups do not react with either of the reactants to a greater extent than the reactants do with each other. Besides being inert to the system and, preferably, being a solvent for the product, the organic solvent must be a solvent for at least one of the reactants, preferably for both of the reactants. The normally liquid organic sol- Vents of the N,N-dialkylcarboxylamide class are useful as solvents in the process of this invention. The preferred solvents are the lower molecular Weight members of this class, particularly N,N-dimethylformamide and N,N-dimethylacetamide. They may easily be removed from the polyamide-acid and/or polyamide-acid shaped articles by evaporation, displacement or diffusion. Other typical compounds of this useful class of solvents are: N,N-diethylformamide, N,N-diethylacetamide, N,N-dimethylmethoxy acetamide, N-methyl. caprolactam, etc. Other solvents which may be used in the present invention are: dimethylsulfoxide, N-methyl-Z-pyrrolidone, tetramethylene urea, pyridine, dimethylsulfone, hexamethylphosphoramide, tetramethylene sulfone, formamide, N-methylformamide and N-acetyl-2-pyrrolidone. The solvents can be used alone, in combinations of solvents, or in combination with poor solvents such as benzene, benzonitrile, dioxa-ne, butyrolactone, xylene, toluene and cyclohexane.

This invention will be more clearly understood by referring to the examples which follow. These examples, which illustrate specific embodiments of the present invention, should not be construed to limit the invention in any way.

Example 1 A 0.2 g. sample of the polyamide from 3,3-dimethoxybenzidine and isophthaloyl chloride, the polymer having an inherent viscosity of 2.0 zit-0.5% in concentrated sulfuric acid at 30 C., in N,N-dimethylacetamide is cast as a film and then heated at 400-430 C. at less than 0.1 pressure for 4 hours. After cooling, the amber solid product is found to be completely insoluble in N,N- dimethylacetamide, in contrast to the original polyamide which is quite soluble. From this and infrared scans it is concluded that the polyamide has been converted to the desired polybenzoxazole.

Example 2 A 10.8 g. portion of 3,3'-dihydroxybenzidine (0.05 mole) is dissolved in 40 ml. of dry N,N-dimethylacetamide under an atmosphere of dry nitrogen. To this is added with stirring 10.15 g. (0.05 mole) of pure isophthaloyl chloride. The solution becomes greenish and quite viscous. Twenty ml. of N,N-dimethylacetamide is used to wash in the last traces of the acid chloride. The mixture is stirred for 25 minutes at room temperature, whereupon it becomes so viscous that further stirring is impossible. The reaction mixture is rapidly extracted three times with 400 ml. portions of sodium bicarbonate solution in a Waring Blendor, then three times each with water, 23 alcohol and dry ether, and then vacuum dried for 12 hours at 25 C. at less than 1 mm. pressure. The product is a green powder which is swelled, but not completely dissolved, by N,N-dimethylacetamide or N-methyl pyrrolidone. The product has an inherent viscosity of 2.3 at 0.5% in concentrated H 50 at 30 C. Its polyamide structure is confirmed by infrared examination.

A mixture of 5 g. of the powdered poly(hydroxyamide) prepared as described above and 95 g. of hexamethylphosphoramide is stirred at 60 C. for 30 minutes, then cooled and filtered through a 200 mesh screen. The solution is degassed by centrifuging and cast on Pyrex glass plates into 15-20 mil layers which are evaporated in a forced draft oven at 120 C. for 30-45 minutes. The partially dried films are then stripped from the glass, clamped to frames and vacuum dried at 100120 C. The resulting films are yellow, tough and creaseable.

One of these films is heated at 430 C. for 3 hours in a forced draft oven under nitrogen. This converts it to a creaseable, amber film. It is confirmed by infrared examination that the poly(hydroxy amide) has been converted to the desired polybenzoxazole structure.

Another poly(hydroxyamide) film is heated for 3 hours at 400 C. at a pressure less than 1 mm., likewise producing a creaseable, amber polybenzoxazole film.

Still another film prepared as described above is dried for only 45 minutes at 120 C. This is heated at 370 C. for 72 hours at less than 1 mm. pressure, producing a creaseable, amber film having an inherent viscosity of 0.59.

Example 3 A solution of 5.70 g. of 3,3'-dimethoxybenzidine in 225 ml. of water and 200 ml. of tetrahydrofuran containing 5.30 g. of anhydrous sodium carbonate is made in a Waring Blendor at room temperature. Then a solution of 4.78 g. of isophththaloyl chloride in 75 ml. of tetrahydrofuran is added rapidly (23 seconds). After agitation for 5 minutes the dimethoxy polyamide is separated by filtration, washed and dried. The yield is 8.0 g. (91.5%) of polymer having an inherent viscosity in sulfuric acid of 2.07. A solution in N,N-dimethylformamide is cast as films, which, on drying are clear and tough.

Examples 4-14 The corresponding polybenzoxazole film of good quality is produced by substituting each of the following aromatic diacid chlorides for isophthaloyl chloride in the procedure of Example 2:

terephthaloyl chloride; biphenyl-3,3'-dicarbonyl chloride; biphenyl-4,4'-dicarbonyl chloride;

bis (3 -chlorocarbonylphenyl) methane; 2,2-bis(3-chlorocarbonylphenyl)propane; naphthalene-2,6-dicarbonyl chloride;

8 naphthalene-1, 8-dicarb onyl chloride; bis 3-chlorocarbonylphenyl) sulfone; bis (3 -chlorocarbonylphenyl) ketone; bis 4-chlorocarbonylphenyl) ketone; and bis (3 -ch1orocarb onylphenyl) sulfone.

Examples 15-25 A film of good quality composed of the corresponding polybenzox-azole results from substituting each of the following dihydroxy diamines for 3,3'-dihydroxybenzidine in the procedure of Example 2:

bis 3-amino-4-hydroxyphenyl) sulfone; bis 3-amino-4-hydroxypheny-l) sulfide; bis 3-amino-4-hydroxyphenyl ether;

bis 3-amino-4-hydroxyphenyl methane; bis (4-amino-3 -hydroxyphenyl) sulfone; bis 4-amino-3-hydroxyphenyl) sulfide; bis (4-amino-3 -hy-droxyphenyl) ether;

bis (4-amino-3-hydroxyphenyl) methane; 1,5 -diamino-2,6-dihydroxynaphthalene; 1,5-diarnino-4,8-dihydroxynaphthalene; and 1,4-diamino-5,8-dihydroxynaphthalene.

What is claimed is: 1. A polymer composed of the structural formula XO OX l l CN/ \NG R Ll i 1'. J.

wherein R is an aromatic tetravalent radical selected from the group consisting of where Y is selected from the group consisting of alkylene, alkylidene, perfluoroalkylene, perfluoroalkylidene, oxygen, sulfur,

where R is selected from the group consisting of hydrogen and lower alkyl; each nitrogen atom being attached directly to a carbon atom of a ring of the aromatic tetravalent radical ortho or peri to the carbon atom to which an --OX is directly attached; R is selected from the group consisting of and ' 9 where Z is selected from the group consisting of alkylene of 1 to 3 carbon atoms, oxygen, sulfur, and SO X is selected from the group consisting of hydrogen,

33 33 as m 3-3 wherein Y is selected from the group consisting of alkylene, alkylidene, perfiuoroalkylene, perfluoroalkylidene, oxygen, sulfur,

where R is selected from the group consisting of hydrogen and lower alkyl; (2) with at least one aromatic dicarboxylic acid-halide in an organic solvent for at least one reactant, the organic solvent being inert to the system, while maintaining the temperature during the reaction below 275 C.

4. A process of preparing a polybenzoxazole which comprises heating the polyamide polymer of claim 1 at a temperature of at least 275 C. for a time sutficient to convert the polyamide polymer to the corresponding polybenzoxazole.

5. The process of claim 3 in which R is the aromatic nucleus in a diamine selected from the group consisting of 3,3-dihydroxybenzidine, bis 3-amino-4-hydroxyphenyl sulfone, bis 3-amin0-4-hydroxyphenyl) sulfide, bis 3-amino-4-hydroxyphenyl) ether, bis 3-a-min o-4-hydroxyphenyl) methane, bis (4amino-3-hydroxyphenyl) sulfone,

bis 4-amino-3 -hydroxyphenyl) sulfide,

bis 4-amino-3 -hydroxyphenyl) ether,

bis (4-amino-3 -hydroxyphenyl) methane, 1,S-diamino-Z,6-dihydroxynaphthalene, 1,5-diamino-4,8-dihydroxynaphthalene, and 1,4-diamino-5,8-dihydroxynaphthalene, and said diacidhalide is selected from the group consisting of isophthaloyl chloride,

terephthaloyl chloride, biphenyl-3,3dicarbonyl chloride, biphenyl-4,4'-dicarbonyl chloride, bis(3-chlorocarbonylphenyl)methane, 2,2-bis (3 -chlorocarb onylphenyl) propane, naphthalene-2,G-dicarbonyl chloride, naphthalene-1,8-dicarbonyl chloride,

bis 3-chlorocarbonylphenyl) sulfone,

bis 3 -chlorocarbonylphenyl) ketone, his(4-chlorocarbonylphenyl)ketone, and his(3-chlorocarbonylphenyl)sulfone.

6. A process as in claim 4 wherein said polyamide polymer is heated in the shape of a self-supporting film.

References Cited UNITED STATES PATENTS 3,094,511 6/ 1963' Hill et al 260 -7 8 3,230,196 1/ 1966 Moyer 260 -47 FOREIGN PATENTS 1,0?) 8,279 9/ 8" Germany.

OTHER REFERENCES Kubota et al.: Journal of Polymer Science, Part B, vol. 2, pp. 655-659, 1964.

WILLIAM H. SHORT, Primary Examiner.

SAMUEL H. BLECH, H. D. ANDERSON,

Assistant Examiners. 

1. A POLYMER COMPOSED OF THE STRUCTURAL FORMULA 